An electrochemical pixel device based on an organic and electrochemically active material is described, e.g. by P. Andersson et al., in “Printable All-Organic Electrochromic Active-Matrix Displays”, Advanced Functional Materials, volume 17, number 16, pp. 3074-3082 (2007). The pixel device is formed by combining an electrochemical transistor with an electrochromic display cell in a side by side arrangement. Furthermore, the electrochemical transistor and the electrochromic display cell are formed of the same organic and electrochemically active material, which, in combination with the side by side arrangement, make possible a display that is very cost effective and simple to manufacture e.g. in a roll-to-roll production procedure. Also, the cost and the complexity of the manufacturing process are reduced due to that only a low number of printing steps and a low number of materials are required.
A drawback of the described display device relates to the electrochemical transistor. Since the electrochemical transistor elements change colour during the switching operation associated with the control of each pixel device, as a result, the perception of a display formed of a number of pixel devices may be disturbed by an electrochromic interference from the transistors. The total viewable colour changing portion of each pixel device in a display arrangement is also affected due to that the area occupied by the electrochemical transistor is limiting the available area for the colour changing portion of the pixel device.
In order to address above drawbacks, alternative architectural configurations that involve manufacturing of vertical structures of a plurality of stacked layers of electrochemical and electrochromic material have been suggested. However, the manufacturing of that type of alternative architectural designs involves further drawbacks. After having considered the demands on precision and stability the suggested architectural configurations would require of the manufacturing process, in order to ensure that all the different layers are in correct alignment with each other in the finished product, the suggestions have been rejected as too complex to achieve, and rendering a too expensive product. The suggested architectures have also been rejected due to poor structural stability which would lead to devices with poor quality and low functional reliability.